This invention relates to a timing sensor for an engine and more particularly to an improved engine camshaft timing sensor.
As is well known, in many forms of engine control it is necessary or desirable to provide a signal indicative of the actual rotational position of the crankshaft and/or the position of the piston within its stroke. Although crankshaft sensors may be utilized for this purpose, the crankshaft of the engine is normally located in an area that is relatively inaccessible and which is also exposed to foreign elements and thus subject to contamination. Thus, if the sensor is mounted in this area, its servicing, access, and inspection can be difficult.
It has, therefore, been proposed to mount a sensor in proximity to the camshaft or one of the camshafts of the engine. As is well known, the camshafts rotate at a timed relationship to the crankshaft. Thus a camshaft sensor will provide substantially the same information as a crankshaft sensor. In addition, the camshafts are normally located in a point that is more accessible on the engine and also one which is less exposed to the environment.
Most high-performance engines employ overhead camshafts in which either one or more camshafts are rotatably journaled in the cylinder head for operating the valves therein. Thus, it has been proposed, as shown in U.S. Pat. No. 5,293,776, issued Mar. 15, 1994, in the names of Masaki Takegami and Hideaki Ueda which patent is assigned to the assignee hereof, to mount a sensor in the cam cover for the engine so that its probe is juxtaposed to the camshaft and can provide a signal indicative of the engine timing. Although this type of device is very acceptable and also positions the sensor so that it can be easily accessed, the cam cover itself may require a mounting of the sensor so that it is spaced a rather substantial distance from the portion of the camshaft with which it cooperates to provide the signal. Hence, weak or inaccurate signals may result.
It has also been proposed to mount the camshaft sensor directly in the cylinder head in closer proximity to the camshaft. Such arrangements have a number of disadvantages. First, if the sensor is mounted in the cylinder head, it is necessary to machine an opening in the cylinder head for the sensor. This added machining to the cylinder head increases its cost and also adds to its complexity. Also, if the engine has intake and exhaust camshafts, then the sensor must be mounted in proximity to one of these camshafts.
The intake camshaft is normally provided adjacent the intake manifold, fuel injectors, and various other components associated with the induction system. Hence, the positioning of the sensor on this side can present some difficulty and interference with other components.
On the other hand, if the sensor is positioned on the exhaust side of the cylinder head, then it is in a more heated area where it may be damaged.
It is, therefore, a principal object of this invention to provide an improved engine sensor and mounting arrangement therefor.
It is a further object of this invention to provide an improved arrangement for mounting a sensor in proximity to the camshaft of an engine and wherein the aforenoted difficulties can be avoided.
It is a still further object of this invention to provide an improved engine camshaft sensor for sensing engine crank angle.
This invention is adapted to be embodied in an internal combustion engine having an engine casting in which a camshaft for operating valves associated with the engine is rotatably journaled. The camshaft is provided with at least one bearing surface that is engaged by a bearing cap for rotatably journaling the camshaft to an engine casting to which the bearing cap is affixed. A timing sensor is detachably affixed to this bearing cap and has a sensing portion juxtaposed to the camshaft for outputting a signal indicative of the position of the camshaft and, accordingly, the engine output shaft.
In accordance with another feature of the invention, the engine casting is provided with a removable closure for closing the area in which the bearing cap is mounted. This cover has an opening through which the sensor extends for removal of the sensor without removing the cover.